Method and device for treating bottom-hole zones of oil-and-gas-bearing formations

ABSTRACT

The invention relates to the field of the oil producing industry and particularly to apparatus the cleaning of face zones and filters of gas-and-oil-producing and water-injection wells. 
     Described is a method for processing bottom-hole zones of oil-and-gas-bearing formations, which method comprising steps of: pumping fluid into the wellbore, then, supplying instantly and unconstrainedly, via supplying lines using the pneumatic generator, a compressed gas agent onto the wellbore fluid mirror, which is accompanied with forming a gas cushion, thereby creating compression waves with sharp edges in said fluid, which waves carry energy with high fluid density along the wellbore with a slight attenuation and ensure a high disjoining pressure that ensures opening of filtration channels of the formation, then exhausting instantly the compressed gas agent, thereby creating dilatation wave with a sharp edge that forms a cavitation pocket in said fluid and ensures an ejection of bridging particles from the formation into the well. 
     Described is an apparatus for processing bottom-hole zones of oil wellbores, which apparatus comprising a wellbore fluid supplying line provided with the valving, a pneumatic generator, compressed gas agent supplying lines provided with quick-operating valving, and a system for exhausting compressed gas agent having gating elements, wherein the pneumatic generator includes a hollow well head comprising an exhaust outlet and an end wall, with the generator open end mounted on the wellbore, into which the compressed gas flows via compressed gas agent supplying lines. 
     On application of this invention, the technical result is in increasing the high-quality and reducing the period of cleanup of bottom-hole zones of producing wells of oil deposit, as well as in improving the apparatus properties concerned with ecology.

The invention relates to the field of the oil producing industry and particularly to the cleaning of face zones and filters of gas-and-oil-producing and water-injection wells.

Known is the installation for processing bottom-hole zones of gas and oil producing and water-injection wells, said installation comprising the wellbore fluid supplying line provided with the valving, pneumatic generator of compression-dilatation waves, compressed gas agent supplying line, system for exhausting compressed gas agent, piston block with gating elements, and said installation having windows in its side wall for exhausting compressed gas agent from the well head chamber (SU 1373024, E21B 43/25, 1991). The specification of this known document describes the method for processing bottom-hole zones of gas-and-oil-bearing formations, wherein the fluid is pumped into the well and then a impact action is performed creating compression-dilatation waves in the wellbore fluid.

The prior art installation has the following disadvantages:

1) a low efficiency of the method for cleaning due to impossibility to create compression-dilatation waves with sharp edges in the wellbore fluid;

2) the installation has no protection means from unconventional situations, specifically from ejection of oil-and-gas shows from the formation into open atmosphere, which makes this installation dangerous in terms of ecology.

The technical result that could be achieved in employing the present method and apparatus for implementing therein, is in ensuring high-quality cleanup of formation bottom-hole zone and high-quality action onto the formation. The additional technical result that could be achieved in employing the present apparatus, is in improving the apparatus properties concerned with ecology.

In order to achieve said technical result, a method for processing bottom-hole zones of oil-and-gas-bearing formations is provided, which method comprising steps of: pumping fluid into the wellbore, supplying instantly and unconstrainedly, via supplying lines using the pneumatic generator, a compressed gas agent onto the wellbore fluid mirror, which is accompanied with forming a great excess pressure of the compressed gas agent at the wellbore fluid surface (gas cushion). In the case of such instant supplying the compressed gas agent, compression waves with sharp edges are formed in said fluid, which waves carry energy with high fluid density along the wellbore with a slight attenuation and ensure a molecule transition of fluid saturating the collecting formation into a state of strong interaction, which results in high disjoining pressure. This pressure exceeds many times the formation pressure, which ensures opening of filtration channels of the formation. Then follows a step of exhausting instantly the compressed gas agent, which creates dilatation wave with a sharp edge that forms a cavitation pocket in fluid and ensures an ejection of bridging particles from the formation into the well.

It is possible to ensure a sharp edge of compression-dilatation waves using various techniques, particularly using gating elements made in the form of quick-operating valving and mounted at lines for supplying compressed gas agent and system for exhausting compressed gas agent and emptying the wellbore space from structure elements of pneumatic generator etc. In order to enhance the effect of compression-dilatation having sharp edge, it is possible to create a suction effect using various technical means and decisions, which facilitates an acceleration of exhausting the compressed gas agent and impurities from the wellbore space.

In order to realize the claimed method, an apparatus for processing bottom-hole zones of oil-and-gas-bearing formations is proposed, which apparatus comprising a wellbore fluid supplying line provided with the valving, a pneumatic generator, compressed gas agent supplying lines, a system for exhausting compressed gas agent having gating elements, wherein the pneumatic generator includes a well head having full-opening cross-section (a hollow well head) and comprising an exhaust outlet and an end wall, with the generator open end mounted on the wellbore, into which the compressed gas flows via compressed gas agent supplying lines, and the valving of the compressed gas agent supplying line being made in the form of quick-operating valving.

As another embodiment of the invention, an apparatus for processing bottom-hole zones of oil-and-gas-bearing formations is proposed, which apparatus comprising a wellbore fluid supplying line provided with the valving, a pneumatic generator, compressed gas agent supplying lines, a system for exhausting compressed gas agent having gating elements, wherein the pneumatic generator includes a well head having full-opening cross-section (a hollow well head) and comprising an exhaust outlet and an end wall, with the generator open end mounted on the wellbore, into which the compressed gas flows via compressed gas agent supplying lines, wherein the hollow well head having at least one acceleration nozzle for the compressed gas agent built in the exhaust outlet, and the valving of the compressed gas agent supplying line being made in the form of quick-operating valving.

Emptying the wellbore space from structure elements of pneumatic generator etc. makes it possible to input, through said space to the bottom hole or into the interval of the bottom-hole zone of oil formation, an instrumentation survey equipment in order to monitor the cleanup process, and acoustic waveguides for additional impact onto the wellbore, which broadens significantly the possibilities of the claimed technical solution.

It should be specifically noted that the step of feeding compressed gas agent onto the wellbore fluid mirror and exhausting it from the wellbore space is performed in a fraction of second, preferably not more than 0.5 s.

It is possible to employ water, Cenomanian, kill fluids, particularly sulphate and carbonate solutions, various hydrocarbon liquids of natural and synthetic origin as the fluid pumped into the wellbore. Chemically inactive gases, preferably technical nitrogen and CO₂, are employed as the compressed gas agent.

Processing of bottom-hole zones of oil-and-gas-bearing formations could be done through one compression-dilatation cycle, or two or more compression-dilatation cycles depending on a type of oil-and-gas-bearing formation and condition of its bottom-hole zone. The condition of bottom-hole zone is determined using special instrumentation survey equipment being descended into the formation through the wellbore space.

Particularly, an acoustic impact onto the wellbore is additionally carried out, particularly an ultrasonic impact.

In a preferable embodiment, the apparatus includes an expansion drum which has a flow area exceeding a flow area of the exhaust outlet and is provided with at least one deferent pipe that forms, together with the exhaust outlet, a system for exhausting compressed gas agent from the well head space. Particularly, the system for exhausting compressed gas agent from the well head space is provided with at least one acceleration nozzle.

Preferably, the system for exhausting compressed gas agent is made coaxial in the well head end wall.

In the preferable embodiment, the apparatus includes at least one acceleration nozzle built in the exhaust outlet coaxially with this outlet. It is reasonable mount at least one acceleration nozzle coaxially in the exhaust outlet with a gap relative to its cross-section.

It is possible to mount at least one acceleration nozzle axially at the well head end wall above the exhaust outlet, particularly with a gap along the outlet axis.

In the case of using several acceleration nozzles, they could be mounted in the exhaust outlet or above it. One of nozzles could be mounted in the exhaust outlet, and others above it.

It is preferable to perform at least one acceleration nozzle having perforated walls.

Preferably, the acceleration nozzle has a flow area of its lower flared end equal to the flow area of the exhaust outlet and is made in the form of conic frustum or Laval nozzle.

Preferably, the exhausting system comprises a pipe branch mounted coaxially in the well head end wall, and the expansion drum is disposed at the upper end of the pipe branch.

Preferably, the gating elements of the exhausting system are made in the form of quick-operating valving and built into either the exhaust outlet of the hollow well head, or the pipe branch between the well head end wall and expansion drum, or the upper end of the pipe branch, or the acceleration nozzle, particularly narrow cross-section of Laval nozzle or one of its flared ends.

Preferably, the exhaust outlet is adequate to the flow area of the well head end wall.

Preferably, the at least one deferent pipe is made in the form of branched system of at least two deferent pipes, wherein the overall flow area of all deferent pipes is not less than the flow area of the expansion drum.

Preferably, the exhausting system is provided with a receiving container for the deferent pipe system, particularly it could be provided with receiving containers for every pipe. Here, the receiving containers could be done hermetical, and the deferent pipes built into those containers. Preferably, at least one of deferent pipes is provided with a make-and-brake joint and high-pressure hydraulic aggregate mounted with a possibility to be connected to that pipe in the location of the make-and-brake joint.

Due to modifying the pneumatic generator structure and emptying the wellbore space from the generator elements, as well as implementing the exhaust outlet in the well head end wall, compression-dilatation waves with sharp edges are created in the wellbore fluid. This is achieved by that, in the compression phase, the compressed gas agent is supplied instantly and unconstrainedly onto the wellbore fluid mirror thereby forming a gas cushion, since the well head space is free. In this case, a compression wave with a sharp edge transfers energy with a high flow density along the pipe as a waveguide with an insignificant attenuation and ensures a transition of molecules of fluid saturating the reservoir formation into the state of the strong interaction, which results in a great disjoining pressure. This pressure exceeds many times a rock pressure, which ensures opening of formation filtration channels. The dilatation wave with a sharp edge replacing the compression wave, owing to said modifications in the generator structure, creates a cavitation pocket in fluid and ensures an ejection of bridging particles from the formation into the well. This effect is increased in the case of presence of additional expansion drum that facilitates, because of its great suction effect, an acceleration of exhausting the compressed gas agent, as well as holds the elements of emptying in its pocket and prevents their return into the well head space. Preferably, the expansion drum volume is equal to or greater than the well head volume for enhancing conditions of unhindered exhaust from the well head.

The fact that the exhaust outlet is at significant distance from the wellbore fluid mirror, as well as the quick-operating valving ensure exhausting of the compressed gas agent in a fraction of second and forming the dilatation wave with a sharp edge.

In the proposed apparatus, due to disposing the exhaust generator elements above the exhaust outlet, as well as providing the expansion drum with the branched pipe system, an exhaust of the compressed gas agent is carried out in a closed exhaust line, which make the apparatus ecofriendly.

Because of the presence of receiving containers for deferent pipes, especially in building the deferent pipes into hermetically implemented containers, ingress of cleanup products into atmosphere is excluded.

Presence of make-and-brake joints (of bayonet connection type, nipple connection, etc.) for deferent pipes, in a non-nominal situation (equipment failure, shows of oil and gas, etc.), and also providing at least one of deferent pipes with a high-pressure hydraulic aggregate that could be supplied, in need, to the location of the make-and-brake joint, permit to terminate operatively an unauthorized flowing of well by killing the formation followed by fault repair, which makes also the apparatus more ecofriendly and increases its performance.

Presence of pipe branch under the expansion drum is defined by serviceability of the apparatus, as well as increased distance from the exhaust outlet for more effective operation of the apparatus.

Locations of the quick-operating valving are also defined on the basis of exploitation and technology considerations.

A size of the exhaust outlet is also selected from technological considerations depending on the oil formation permeability, its occurrence depth, etc.

An important result in use the proposed structure scheme in the apparatus is in emptying the well head space, which makes it possible to input, through said space to the bottom hole or into the interval of the wellbottom zone of oil formation, an instrumentation survey equipment and to monitor the cleanup process, which increases the apparatus performance.

The invention is explained by drawings, wherein:

FIG. 1 depicts diagrammatically the main view of the apparatus;

FIG. 2 shows the apparatus cross-section diagram in the compression phase;

FIG. 3 shows the apparatus cross-section diagram in the dilatation phase with the expansion drum mounted on the pipe branch; and

FIG. 4 depicts diagrammatically the main view of the apparatus with the mounted acceleration nozzle.

The apparatus comprises a well head 2 mounted on a wellbore 1 coaxially with the well 1, said well head 2 having an end wall 3 with an exhaust outlet 4 in the upper part. Into the side wall of the well head 2 are built a wellbore fluid supplying line 5 with a valving 6 and a compressed gas agent supplying line 7 with a valving 8 from a receiver 9. the drawings represent a variant of disposing an expansion drum 10 coaxially with the well head by means of a pipe branch 11, which forms a line for exhausting the compressed gas agent through pipes 12, 13, 14 into receiving containers 15, 16, 17. Deferent pipes (at least one of them) are provided with a make-and-brake joint 18 in order to prevent non-nominal situations. A quick-operating valving 19 and acceleration nozzles 20 are built into the exhausting line or exhaust outlet 4.

The quick-operating valving 19 is shown in FIGS. 1, 2, 3 in different variants of its location in the exhaust system in the exhaust outlet, which is determined, in each case, by technological considerations depending on a well type, a formation occurrence depth (that could reach 4 km), computational considerations, etc. The quick-operating valving could be implemented in the form of electrovalve, electromagnetic valve, pneumatic valve, etc., ensuring operation speed less than 1 sec. The quick-operating valving 19 could be built into the pipe branch between the well head end wall and expansion drum (FIG. 1) or into the exhaust outlet of the hollow well head (FIG. 2), or into the upper end of the pipe branch (FIG. 3), The width of the exhaust outlet and location of the expansion drum are defined by the same considerations.

The make-and-brake joint 18 is implemented by any known connection, for example, in the form of bayonet clamp, etc., for supplying quickly a high-pressure hydraulic aggregate to the pipe branch and supplying a fluid into that pipe in the location of the make-and-brake joint for terminating an unauthorized flowing of oil into the well.

The apparatus operates as follows.

The cleanup is performed with alternation, in the wellbore fluid, compression and dilatation waves in every cycle. Depending on a contamination level of the oil formation in the bottom-hole zone, the cleanup could require a series of cycles or should be terminated at one cycle.

Every cycle is implemented as follows. The wellbore 1 is filled with the wellbore fluid via the line 5 with the open valving 6 through the well head 2, whereupon the line 5 is closed by means of valving 6. Then the valving 8 is opened (with the closed valving 19), and the compressed gas agent (a gas inactive in oxidizing reactions, advantageously the technical nitrogen) is supplied via the line 7 into the space of the well head 2. Since the valving 8 is quick-operating, then the compressed gas agent fills instantly the space of the well head 2, creating a pressure onto the wellbore fluid and forming a gas cushion over its mirror. In so doing, a pressure shockwave with a sharp edge is created in the wellbore fluid, being characterized with a high energy flux density and small attenuation and being able to propagate at great distances and create a blast effect onto congestions in the bottom-hole zone of the oil formation. The pressure in the well head is supported constant till arrival of the wave reflected from the bottom of well.

Then the compressed gas agent supplying line is shut off using the quick-operating valving 8 and the exhausting line is opened by means of opening the quick-operating valving 9 (having the operation speed less than 1 sec.). The compressed gas agent from the gas cushion through the exhaust outlet 4 and expansion drum 10 is instantly discharged from the well head 2 via the exhausting line through the deferent pipes 12, 13, 14 into the receiving containers 15, 16, 17.

Herein, due to a pressure difference, a suction effect is created while discharging the compressed gas agent, as well as a partial degassing of the wellbore fluid takes place, which prevents from a simultaneous discharging gas and fluid mixture, increases the speed of discharging the compressed gas agent, and ensures producing the dilatation wave in the wellbore fluid with a sharp edge and creates cavitation pockets. By virtue of presence of the expansion drum 10, this effect is gained, and in this case, while sudden discharge of the compressed gas agent and, after that, subsequent raise of the fluid with the cleanup products, the expansion drum 10 prevents those products from entry into the well head 2 and ensures their lifting through the deferent pipes 12, 13, 14 into the receiving containers 15, 16, 17.

The make-and-brake joint 19 ensures, in a non-nominal situation (an unauthorized flowing of oil, equipment failure, etc.), a quick disconnection of the pipe into which this connection 19 being built, supplying the high-pressure hydraulic aggregate to that zone for killing oil in the wellbore or ensuring the equipment repair.

If it is necessary, cleanup cycles are repeated.

The cleanup result could be determined with the instrumentation survey equipment, for which purpose the instrumentation survey equipment being descended into the bottom-hole of the well head free space (not shown in drawings).

The construction allows executing a high-quality cleanup with the simultaneous process monitoring.

Upon termination of the cleanup process, which is determined according to data of the instrumentation survey equipment, the wellbore fluid is drained into a special storage (pit) in the dilatation phase.

Presence of the make-and-brake joint and high-pressure hydraulic aggregate allow maintaining the apparatus ecofriendly in emergency situation as well. 

1. A method for processing bottom-hole zones of oil-and-gas-bearing formations, which method comprising steps of: pumping fluid into the wellbore, then accomplishing an impact action onto the formation by supplying instantly and unconstrainedly, via supplying lines using the pneumatic generator, a compressed gas agent onto the wellbore fluid mirror, which is accompanied with forming a gas cushion, thereby creating compression waves with sharp edges in said fluid, which waves carry energy with high fluid density along the wellbore with a slight attenuation and ensure a high disjoining pressure that ensures opening of filtration channels of the formation, then exhausting instantly the compressed gas agent, thereby creating dilatation wave with a sharp edge that forms a cavitation pocket in said fluid and ensures an ejection of bridging particles from the formation into the well.
 2. The method according to claim 1, wherein compression-dilatation waves with sharp edges are created using gating elements made in the form of quick-operating valving. 3-6. (canceled)
 7. The method according to claim 1, wherein condition of bottom-hole zone is determined using an instrument.
 8. (canceled)
 9. The method according to claim 1, wherein an acoustic impact onto the wellbore is carried out additionally. 10-11. (canceled)
 12. An apparatus for processing bottom-hole zones of oil-and-gas-bearing formations, the apparatus comprising a wellbore fluid supplying line provided with the valving, a pneumatic generator of compression-dilatation waves, compressed gas agent supplying lines, and a system for exhausting compressed gas agent having gating elements, wherein the pneumatic generator includes a well head having full-opening cross-section, an exhaust outlet and an end wall, with the generator open end mounted on the wellbore, into which the compressed gas flows via compressed gas agent supplying lines, and the valving of the compressed gas agent supplying line being made in the form of quick-operating valving.
 13. The apparatus according to claim 12, characterizing in that the apparatus includes an expansion drum which has a flow area exceeding a flow area of the exhaust outlet and is provided with at least one deferent pipe that forms, together with the exhaust outlet, a system for exhausting compressed gas agent from the well head space. 14-17. (canceled)
 18. The apparatus according to claim 13, wherein the quick-operating valving of the exhausting system is built into a pipe branch between the well head end wall and expansion drum.
 19. (canceled)
 20. The apparatus according to claim 12, wherein the exhaust outlet is adequate to the flow area of the well head end wall. 21-24. (canceled)
 25. The apparatus according to claim 13, wherein at least one of the deferent pipes is provided with a make-and-brake joint and high-pressure hydraulic aggregate mounted with a possibility to be connected to said pipe into the location of the make-and-brake joint.
 26. An apparatus for processing bottom-hole zones of oil-and-gas-bearing formations, which apparatus comprising a wellbore fluid supplying line provided with the valving, a pneumatic generator, compressed gas agent supplying lines, and a system for exhausting compressed gas agent having gating elements, wherein the pneumatic generator includes a well head having full-opening cross-section and comprising an exhaust outlet and an end wall, with the generator open end mounted on the wellbore, into which the compressed gas flows via compressed gas agent supplying lines, wherein the hollow well head having at least one acceleration nozzle for the compressed gas agent built in the exhaust outlet, and the valving of the compressed gas agent supplying line being made in the form of quick-operating valving.
 27. The apparatus according to claim 26, wherein at least one acceleration nozzle is built into the exhaust outlet coaxial with this outlet. 28-29. (canceled)
 30. The apparatus according to claim 26, wherein at least one acceleration nozzle is mounted above the exhaust outlet coaxial and with a gap along the outlet axis.
 31. The apparatus according to claim 26, wherein the acceleration nozzles are mounted in the exhaust outlet and above this outlet.
 32. (canceled)
 33. The apparatus according to claim 26, wherein at least one acceleration nozzle is made with perforated walls. 34-35. (canceled)
 36. The apparatus according to claim 26, wherein at least one acceleration nozzle is made in the form of Laval nozzle.
 37. The apparatus according to claim 26, wherein the apparatus includes an expansion drum that has a flow area exceeding a flow area of the exhaust outlet and is provided with at least one deferent pipe that forms, together with the exhaust outlet, a system for exhausting compressed gas agent from the well head space.
 38. (canceled)
 39. The apparatus according to claim 26, wherein the gating elements of the exhausting system are made in the form of quick-operating valving. 40-46. (canceled)
 47. The apparatus according to claim 26, wherein the exhaust outlet is adequate to the flow area of the well head end wall. 48-50. (canceled)
 51. The apparatus according to claim 37, wherein at least one of deferent pipes is provided with a make-and-brake joint and high-pressure hydraulic aggregate mounted with a possibility to be connected to said pipe into the location of the make-and-brake joint. 